This invention relates in general to solenoid operated control valves and deals more particularly with the valves which have a spring pressed valve member and a solenoid for displacing the valve member such as disclosed on U.S. Pat. Nos. 3,013,768 and 4,027,850.
The valves foredescribed are desired to be small, light and vibration-resistant for installing them on automotive vehicles. The valves may become relatively light and vibration-resistant by reducing the weight of the armature assembly of the valves. However the reduction of the weight of the armature assembly gives rise to variations in the compression force of a spring against a valve member of the armature assembly, which cause the valve member an inclined slight eccentricity against a valve seat to which the valve member is yieldably urged by the compression force of the spring. The eccentricity loosens the intimate closure of an opening of the valve seat with the valve member.
Accordingly, hitherto known solenoid valves have an elongated magnetic plunger for eliminating the eccentricity. One of the valves is shown in FIG. 1. The solenoid valve shown in FIG. 1 has an elongated hexagonal plunger 3 slidably fitted in a cylindrical bobbin 8. A solenoid 2 is mounted on the bobbin 8. The plunger 3 has sealing elements 4a and 4b at its opposed ends. The interior surface of the bobbin 8 surrounds a main elongated portion of the plunger 3 to guide its movement toward and away from valve seats 5a and 5b without inclination of the plunger 3 whereby to abut the sealing element 4a and 4b concentric with the valve seats 5a and 5b respectively. The plunger 3 is normally urged toward the valve seat 5b by a spring 6 as shown in FIG. 1 whereby the sealing element 4a is away from the valve seat 5a and the sealing element 4b abuts on the valve seat 5b. A port 7 communicates with a port 9 through a gap between the sealing element 4a and the valve seat 5a as well as a clearance between the outer surface of the hexagonal plunger 3 and the interior surface of cylindrical bobbin 8. When the solenoid 2 is energized the plunger 3 moves toward the valve seat 5a against the action of the spring 6 whereby the sealing element 4a abuts on the valve seat 5a and the sealing element 4b is away from the valve seat 5b. Thus the communication between the ports 7 and 9 is interrupted.
The valve 1 is relatively lengthy and heavy because it has elongated solid plunger 3. Thus the employment of the elongated plunger contradicts the requirements that the valves should be small, light and vibration-resistant for the use of automotive vehicles. Although the plunger may be a hollow or cylindrical one, the diameter of the cylindrical plunger should be large enough to maintain a predetermined magnetic reluctance. Thus the plunger and the valves may become bulky.